The present invention relates to a digital data recording apparatus, and in particular, to a digital data recording apparatus, which records a recording data on a magnetic tape using a rotary head.
In the case of handling digital information via a magnetic recording unit, there is a need of recording a binary information having logical values xe2x80x9c1xe2x80x9d and xe2x80x9c0xe2x80x9d on a magnetic medium without an error, and regenerating the binary information recorded from the magnetic medium without an error. In this case, a pulse string having binary information, that is, logical values xe2x80x9c1xe2x80x9d and xe2x80x9c0xe2x80x9d is converted into a recording data by an encoder, and a rectangular wave current corresponding to the recording data flows through a recording head. By doing so, a recording signal having a pulse string of logical values xe2x80x9c1xe2x80x9d and xe2x80x9c0xe2x80x9d is recorded in accordance with the presence or absence of magnetization reversal on the magnetic medium. Further, when regenerating, the presence of regenerative pulse signal at a predetermined time zone is detected based on a synchronizing signal, and then, the recording signal is regenerated by a decoder based on the detected pulse string.
In this case, a recording data is converted by the encoder when recording, and the minimum continuation length Tmin of the logical value xe2x80x9c1xe2x80x9d of the obtained recording data receives a limitation by a pulse interference generated in recording/regenerating process. For this reason, the minimum continuation length Tmin is hard to be set to a predetermined value or less. On the other hand, the maximum continuation length Tmax influences a synchronizing ability successively self-corrected by a regenerative detection pulse generated at the logical value xe2x80x9c1xe2x80x9d of the recording data, and a so-called low frequency cut-off is generated in signal transmission by a rotary transformer.
Moreover, in this type of digital data recording apparatus, in a high transfer rate, an edge portion of waveform pattern of recording current weakens by a permeability of the recording head and frequency characteristics of a recording amplifier; as a result, a high frequency component is deteriorated. For this reason, a phase of a short wavelength side is delayed with respect to a long wavelength side of a magnetizing pattern recorded on a magnetic tape, and therefore, a so-called peak shift occurs as well known.
In order to solve the problem of the low frequency cut-off by the rotary transformer of the above conventional digital data recording apparatus, the following system has been proposed. According to the system, the recording data is modulated at a recording clock, and then, is transmitted by a rotary transformer in a state of having no direct current component, and further, is demodulated using a delay line corresponding to a data rate. However, according to this method, in the case where the data rate is greatly variable, the configuration of the system becomes complicated, and it is impossible to perform a highly accurate demodulating operation.
Moreover, in order to suppress the peak shift to the lowest limitation, the following system has been proposed. According to the system, resonance of the recording head and an HPF are used, and thereby, a high frequency component of recording data is enhanced. However, according to this system, it is impossible to suitably adapt to variations of data rate.
The present invention has been made in view of the above problem of this type of digital recording apparatuses in the prior art. Therefore, an object of the present invention is to provide a digital data recording apparatus, which can transmit a recording data via a rotary transformer without receiving an influence of the recording data rate and low frequency cut-off, and can suitably enhance a high frequency component of the recording data in accordance with the recording data rate, and further, has a simple configuration.
A digital data recording apparatus of the present invention comprises:
modulation means for modulating a recording clock by a recording data;
reference level setting means for setting a reference voltage and a reference current in signal processing based on a reference clock having a multiple cycle of the cycle of the recording clock when the reference clock is supplied via a signal transmission line having low frequency cut-off characteristics;
demodulation means for obtaining a demodulation signal from a modulation signal when the modulation means supplies the modulation signal via the signal transmission line having low frequency cut-off characteristics;
recording signal generating means for generating a recording signal from the demodulation signal; and
recording means for recording the recording signal on a recording medium,
the demodulation means having: signal forming means for obtaining a modulation signal and an inverted modulation signal from the modulation signal; first and second saw-tooth wave generators for obtaining first and second saw-tooth wave signals from the modulation signal and the inverted modulation signal when a reference current is supplied from the reference level setting means; and a mixer for mixing the first and second saw-tooth wave signals, and obtaining the demodulation signal based on an output signal from the mixer and the reference voltage from the reference level setting means.
Further, the digital data recording apparatus of the present invention is provided with high frequency enhancement waveform generating means for generating a high frequency enhancement waveform with respect to the demodulation signal, and the high frequency enhancement waveform is superposed on the demodulation signal so as to generate a recording signal.
Further, the digital data recording apparatus of the present invention is provided with envelope detection means for detecting an envelope level of the modulation signal, and a recording current for recording the recording signal on a recording medium is controlled in accordance with the envelope level obtained from the envelope detection means.
According to the present invention, by a simple configuration, the modulation signal of the recording data is transmitted via a signal transmission line having low frequency cutoff characteristics such as a rotary transformer without being influenced by the recording data rate and low frequency cut-off, and the modulation signal after being transmitted via the signal transmission line having low frequency cut-off characteristics is demodulated. Further, a high frequency component of the demodulation signal is properly enhanced in accordance with the recording data rate, and peak shift is prevented with respect to a recording magnetizing pattern to thereby perform high-quality digital recording.